Sort.java

public class Sort { 
    public static void sort(int[] a) { 
        quickSort(a, 0, a.length - 1); 
    } 
    
    static void swap(int[] a, int i, int j) { 
        int temp = a[i];
        a[i] = a[j]; 
        a[j] = temp; 
    } 
    
    static int partition(int[] a, int start, int end) { 
        int value = a[end];
        int i = start - 1;
        for (int j = start; j <= end - 1; ++j) 
            if (a[j] < value) 
                swap(a, ++i, j); 
            swap(a, i + 1, end); 
            return i + 1;
    } 
    
    static void quickSort(int[] a, int start, int end) { 
        if (start >= end) return; 
        int middle = partition(a, start, end); 
        quickSort(a, start, middle-1); 
        quickSort(a, middle+1, end); 
    } 
}